RTOW, in most parlance, is the limiting takeoff weight for the occasion. Its only relevance to the loadsheet is in respect of needing to make sure that the loadsheet TOW does not exceed the RTOW.
That is to say, you should be able to determine RTOW quite independent of the LDS information. I would imagine that your EFB will have provision for you to enter the runway, ambient conditions, etc .. and it should then spit out a value for RTOW ?
Or have I missed your point ?
If your concern is only with payload, then the RTOW will let you figure out your maximum payload, considering ZFW and required fuel load. Actual payload will follow from the LDS information.
I'm sort of reading between the lines and seeing that you might be confusing RTOW with actual TOW ?
I can only imagine that your Type ground course and/or ops eng training associated with the rating training was a tad undercooked ?